Communication devices such as User Equipments (UEs) are also known as e.g. terminals, mobile terminals, wireless terminals and/or mobile stations. User equipments are enabled to communicate wirelessly in a cellular communications network or wireless communication system, sometimes also referred to as a cellular radio system or cellular networks. The communication may be performed e.g. between two user equipments, between a user equipment and a regular telephone and/or between a user equipment and a server via a Radio Access Network (RAN) and possibly one or more core networks, comprised within the cellular communications network.
User equipments may further be referred to as mobile telephones, cellular telephones, laptops, or surf plates with wireless capability, just to mention some further examples. The user equipments in the present context may be, for example, portable, pocket-storable, hand-held, computer-comprised, or vehicle-mounted mobile devices, enabled to communicate voice and/or data, via the RAN, with another entity, such as another terminal or a server.
The cellular communications network covers a geographical area which is divided into cell areas, wherein each cell area is served by a base station, e.g. a Radio Base Station (RBS), which sometimes may be referred to as e.g. “eNB”, “eNodeB”, “NodeB”, “B node”, or BTS (Base Transceiver Station), depending on the technology and terminology used. The base stations may be of different classes such as e.g. macro eNodeB, home eNodeB or pica base station, based on transmission power and thereby also cell size. A cell is the geographical area where radio coverage is provided by the base station at a base station site. One base station, situated on the base station site, may serve one or several cells. Further, each base station may support one or several communication technologies. The base stations communicate over the air interface operating on radio frequencies with the user equipments within range of the base stations. In the context of this disclosure, the expression Downlink (DL) is used for the transmission path from the base station to the user equipment. The expression Uplink (UL) is used for the transmission path in the opposite direction i.e. from the user equipment to the base station. The DL is sometimes also referred to as a forward link, while the UL is sometimes also referred to as a reverse link.
In 3rd Generation Partnership Project (3GPP) Long Term Evolution (LTE), base stations, which may be referred to as eNodeBs or even eNBs, may be directly connected to one or more core networks.
Universal Mobile Telecommunications System (UMTS) is a third generation mobile communication system, which evolved from the GSM, and is intended to provide improved mobile communication services based on Wideband Code Division Multiple Access (WCDMA) access technology. UMTS Terrestrial Radio Access Network (UTRAN) is essentially a radio access network using wideband code division multiple access for user equipments. The 3GPP has undertaken to evolve further the UTRAN and GSM based radio access network technologies.
3GPP LTE radio access standard has been written in order to support high bitrates and low latency both for uplink and downlink traffic. All data transmission is in LTE is controlled by the radio base station.
In ad hoc networking, neighbor discovery refers to a procedure that allows wireless devices in the proximity of each other to detect the presence of one another. Neighbor discovery in ad hoc networks involves an engineering tradeoff between energy efficiency, discovery range, the number of discovered devices and the discovery time. Typically, ad hoc technologies such as Bluetooth deal with this problem by carefully designing beacon signaling procedures and employing state transitions between energy conserving and active, i.e. beacon transmitting and detecting states.
In so called network assisted device discovery, the classical ad hoc discovery process may be enhanced by network signaling so as to provide synchronization between devices, and using network-device signaling that makes devices aware of the reserved resources for beacon signaling and a bit pattern employed by the beacon signals. Such network signaling can thus eliminate beacon collisions and make rendezvous' between advertising and capturing type of devices in time and frequency less time consuming.
However, network assistance through network-device signaling increases the processing load in network nodes and requires a significant amount of spectrum resources and may have scalability problems as the number of devices per cell increases.
Device discovery is a well-known and widely used component of many existing wireless technologies, including ad hoc and cellular networks. Examples include Bluetooth, several variants of the IEEE 802.11 standards suite, such as WiFi Direct. The key technique used by these standards is to use specially designed beacon signals that so called master devices can broadcast and so called slave devices can capture, so that nearby slave devices can detect the proximity as well as some characteristics of such beacon broadcasting devices. Beacon signaling based device discovery requires that the broadcasting and capturing devices meet in the time, frequency and code domains. Furthermore, in order for discovery to work, the slave device capturing beacon signals must be able to decode the information encoded in the beacon signal. In other words, the beacon signal must reach a certain Signal to Interference plus Noise Ratio (SINR) threshold at the capturing slave device in order for it to be useful for device discovery. A device sending beacon signals is referred to as a master device and a device capturing the beacon signals is referred to as a slave device.
Recently, Device-to-Device (D2D) communications as an underlay to cellular networks has been provided as a means to take advantage of the proximity of communicating devices and at the same time to allow devices to operate in a controlled interference environment. Various device discovery techniques applicable for devices in cellular spectrum have also been discussed recently. These techniques make use of various forms of network assistance, such as obtaining synchronization, Peer Discovery Resources (PDR) or tuning other parameters of the discovery process.
Although device discovery for ad hoc networking type of technologies such as Bluetooth, WiFi Direct, etc. is a relatively mature technology, only very few existing techniques have been built for devices operating in cellular spectrum.
There are also a few disclosed solutions discussed for device discovery for devices operating in cellular spectrum considering in general D2D cellular communications as a special type of ad-hoc communication involving only two communicating devices via a direct radio link.
The problem of today's procedure for device discovery is that if there are many master devices in vicinity of each other, they use colliding peer discovery resources for the bacon signals. Such collisions of beacon signals make beacon signals undetectable or not decodable by surrounding slave devices. This make the discovery of such master devices difficult if not impossible by other slave devices in the neighborhood.